PRJ566 Project Planning and Management Lecture: Network Diagrams

To Create a Plan You Need… Work Breakdown Structure Dependencies Milestones The Network Early/Late Start/End dates Slack/Float Critical Path

Task Dependencies Task A is said to be dependent on task B if task B must precede task A (task B must be finished before task A can start) Task B is called a predecessor of task A Task A can have many predecessors Only immediate predecessors are referred to as predecessors

Milestone A task with zero time allocated to it. It is used as a marker; documentation. It is not assigned to anyone. Tasks can be dependent on milestones.

Network Diagram A pictorial representation of the sequence in which the project work can be done Shows the relationships (dependencies!) between tasks MS Project creates network diagrams for you (=Gantt chart in MS Project)

Network Diagram What order do I do these tasks in?

Network Diagram 1.1 Measure Room 1.2 Choose colors 1.3 Create Materials List 1.4 Create Estimate Sheet 1.5 Review with client 2 Purchase Materials 3.1 Move Furniture 3.2 Wash Walls 3.3 Cover Floors 4 Paint Room 5.1 Clean up 5.2 Remove Floor Covers

Network Diagram = Gantt Chart

Why are Network Diagrams important? You can plan more effectively--you can see the relationship between activities Easier to reschedule--you can see impact of changes Allows you to monitor and control the project--compare it against baseline

Calculating Slack/Float What is the earliest/latest possible start of each task?

Slack/Float time Free Slack: range in which task can finish without causing delay in early schedule of immediate successors Total Slack: range in which task can finish without causing delay to project completion

Late and Early Start/Finish Early start/finish--earliest possible time that a task can start/finish without causing delay Late start/finish--latest possible time that a task can start/finish without causing delay

Early Start/Finish ES = latest finish of predecessors + 1 EF = (ES + duration) - 1

Early Start/Finish

Late Start/Finish LF = earliest start of successors - 1 LS = (LF - duration) + 1

Late Start/Finish

Slack/Float time The delay (in units of time) that could be tolerated in starting or completion time of a task without causing a delay in the project. Slack time for a task = LF - EF

Slack Time = LF - EF

Critical Path Longest duration path in network diagram Sequence of tasks whose early and late dates are the same Sequence of tasks with zero slack

Critical Path

Why care about Critical Path? Tasks on this path need to be on time! If you know what they are you can track them!

Critical Path

Critical Path

Dependencies with Lag Time Lag time is time that must elapse after one task is completed before the dependent task can start How do we show this in MSProject? Use the lag time variable in the task definition

These tasks fit all criteria Longest duration path in network diagram Sequence of tasks whose early and late dates are the same Sequence of tasks with zero slack

Why care about Critical Path? Tasks on this path need to be on time! If you know what they are you can track them! You can compress, adjust for maximum benefit

Management Reserve A contingency Budget of time--a time bank 5 to 10 % of total duration Withdraw from it when you run into trouble Monitor it to see how much youre using it (overuse means trouble!)